, an anemone in a 30 gal
is probably not a good idea. In large tanks it is do-able, but still not a good idea. Even if everything goes well with the Anemone and the coral, as is my case, the Anemone will wear out his welcome, because of competition for space, as coyote said.
I've had my Sebae for over 6 years and now is in the front corner of my 180. Just the shroud without the tentacles has to be 14-16" across, clown loves it but it has to be isolated. Luckily for me he isn't really much of a roamer, but he and the Gold-band 'maroon will soon be going. I hate to seperate them so the clown will go too.
With that said, you can still get a clown. Unless it conflicts with other stock, if you want one, get one. If your waters up to snuff and you feed him, he'll be fine!